/*
   * fs/kernfs/inode.c - kernfs inode implementation
   *
   * Copyright (c) 2001-3 Patrick Mochel
   * Copyright (c) 2007 SUSE Linux Products GmbH
   * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
   *
   * This file is released under the GPLv2.
   */
  
  #include <linux/pagemap.h>
  #include <linux/backing-dev.h>
  #include <linux/capability.h>
  #include <linux/errno.h>
  #include <linux/slab.h>
  #include <linux/xattr.h>
  #include <linux/security.h>
  
  #include "kernfs-internal.h"
  
  static const struct address_space_operations kernfs_aops = {
  	.readpage	= simple_readpage,
  	.write_begin	= simple_write_begin,
  	.write_end	= simple_write_end,
  };
  
  static struct backing_dev_info kernfs_bdi = {
  	.name		= "kernfs",
  	.ra_pages	= 0,	/* No readahead */
  	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
  };
  
  static const struct inode_operations kernfs_iops = {
  	.permission	= kernfs_iop_permission,
  	.setattr	= kernfs_iop_setattr,
  	.getattr	= kernfs_iop_getattr,
  	.setxattr	= kernfs_iop_setxattr,
  	.removexattr	= kernfs_iop_removexattr,
  	.getxattr	= kernfs_iop_getxattr,
  	.listxattr	= kernfs_iop_listxattr,
  };
  
  void __init kernfs_inode_init(void)
  {
  	if (bdi_init(&kernfs_bdi))
  		panic("failed to init kernfs_bdi");
  }
  
  static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
  {
  	static DEFINE_MUTEX(iattr_mutex);
  	struct kernfs_iattrs *ret;
  	struct iattr *iattrs;
  
  	mutex_lock(&iattr_mutex);
  
  	if (kn->iattr)
  		goto out_unlock;
  
  	kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
  	if (!kn->iattr)
  		goto out_unlock;
  	iattrs = &kn->iattr->ia_iattr;
  
  	/* assign default attributes */
  	iattrs->ia_mode = kn->mode;
  	iattrs->ia_uid = GLOBAL_ROOT_UID;
  	iattrs->ia_gid = GLOBAL_ROOT_GID;
  	iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
  
  	simple_xattrs_init(&kn->iattr->xattrs);
  out_unlock:
  	ret = kn->iattr;
  	mutex_unlock(&iattr_mutex);
  	return ret;
  }
  
  static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
  {
  	struct kernfs_iattrs *attrs;
  	struct iattr *iattrs;
  	unsigned int ia_valid = iattr->ia_valid;
  
  	attrs = kernfs_iattrs(kn);
  	if (!attrs)
  		return -ENOMEM;
  
  	iattrs = &attrs->ia_iattr;
  
  	if (ia_valid & ATTR_UID)
  		iattrs->ia_uid = iattr->ia_uid;
  	if (ia_valid & ATTR_GID)
  		iattrs->ia_gid = iattr->ia_gid;
  	if (ia_valid & ATTR_ATIME)
  		iattrs->ia_atime = iattr->ia_atime;
  	if (ia_valid & ATTR_MTIME)
  		iattrs->ia_mtime = iattr->ia_mtime;
  	if (ia_valid & ATTR_CTIME)
  		iattrs->ia_ctime = iattr->ia_ctime;
  	if (ia_valid & ATTR_MODE) {
  		umode_t mode = iattr->ia_mode;
  		iattrs->ia_mode = kn->mode = mode;
  	}
  	return 0;
  }
  
  /**
   * kernfs_setattr - set iattr on a node
   * @kn: target node
   * @iattr: iattr to set
   *
   * Returns 0 on success, -errno on failure.
   */
  int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
  {
  	int ret;
  
  	mutex_lock(&kernfs_mutex);
  	ret = __kernfs_setattr(kn, iattr);
  	mutex_unlock(&kernfs_mutex);
  	return ret;
  }
  
  int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
  {
  	struct inode *inode = dentry->d_inode;
  	struct kernfs_node *kn = dentry->d_fsdata;
  	int error;
  
  	if (!kn)
  		return -EINVAL;
  
  	mutex_lock(&kernfs_mutex);
  	error = inode_change_ok(inode, iattr);
  	if (error)
  		goto out;
  
  	error = __kernfs_setattr(kn, iattr);
  	if (error)
  		goto out;
  
  	/* this ignores size changes */
  	setattr_copy(inode, iattr);
  
  out:
  	mutex_unlock(&kernfs_mutex);
  	return error;
  }
  
  static int kernfs_node_setsecdata(struct kernfs_node *kn, void **secdata,
  				  u32 *secdata_len)
  {
  	struct kernfs_iattrs *attrs;
  	void *old_secdata;
  	size_t old_secdata_len;
  
  	attrs = kernfs_iattrs(kn);
  	if (!attrs)
  		return -ENOMEM;
  
  	old_secdata = attrs->ia_secdata;
  	old_secdata_len = attrs->ia_secdata_len;
  
  	attrs->ia_secdata = *secdata;
  	attrs->ia_secdata_len = *secdata_len;
  
  	*secdata = old_secdata;
  	*secdata_len = old_secdata_len;
  	return 0;
  }
  
  int kernfs_iop_setxattr(struct dentry *dentry, const char *name,
  			const void *value, size_t size, int flags)
  {
  	struct kernfs_node *kn = dentry->d_fsdata;
  	struct kernfs_iattrs *attrs;
  	void *secdata;
  	int error;
  	u32 secdata_len = 0;
  
  	attrs = kernfs_iattrs(kn);
  	if (!attrs)
  		return -ENOMEM;
  
  	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
  		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
  		error = security_inode_setsecurity(dentry->d_inode, suffix,
  						value, size, flags);
  		if (error)
  			return error;
  		error = security_inode_getsecctx(dentry->d_inode,
  						&secdata, &secdata_len);
  		if (error)
  			return error;
  
  		mutex_lock(&kernfs_mutex);
  		error = kernfs_node_setsecdata(kn, &secdata, &secdata_len);
  		mutex_unlock(&kernfs_mutex);
  
  		if (secdata)
  			security_release_secctx(secdata, secdata_len);
  		return error;
  	} else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
  		return simple_xattr_set(&attrs->xattrs, name, value, size,
  					flags);
  	}
  
  	return -EINVAL;
  }
  
  int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
  {
  	struct kernfs_node *kn = dentry->d_fsdata;
  	struct kernfs_iattrs *attrs;
  
  	attrs = kernfs_iattrs(kn);
  	if (!attrs)
  		return -ENOMEM;
  
  	return simple_xattr_remove(&attrs->xattrs, name);
  }
  
  ssize_t kernfs_iop_getxattr(struct dentry *dentry, const char *name, void *buf,
  			    size_t size)
  {
  	struct kernfs_node *kn = dentry->d_fsdata;
  	struct kernfs_iattrs *attrs;
  
  	attrs = kernfs_iattrs(kn);
  	if (!attrs)
  		return -ENOMEM;
  
  	return simple_xattr_get(&attrs->xattrs, name, buf, size);
  }
  
  ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
  {
  	struct kernfs_node *kn = dentry->d_fsdata;
  	struct kernfs_iattrs *attrs;
  
  	attrs = kernfs_iattrs(kn);
  	if (!attrs)
  		return -ENOMEM;
  
  	return simple_xattr_list(&attrs->xattrs, buf, size);
  }
  
  static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
  {
  	inode->i_mode = mode;
  	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  }
  
  static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
  {
  	inode->i_uid = iattr->ia_uid;
  	inode->i_gid = iattr->ia_gid;
  	inode->i_atime = iattr->ia_atime;
  	inode->i_mtime = iattr->ia_mtime;
  	inode->i_ctime = iattr->ia_ctime;
  }
  
  static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
  {
  	struct kernfs_iattrs *attrs = kn->iattr;
  
  	inode->i_mode = kn->mode;
  	if (attrs) {
  		/*
  		 * kernfs_node has non-default attributes get them from
  		 * persistent copy in kernfs_node.
  		 */
  		set_inode_attr(inode, &attrs->ia_iattr);
  		security_inode_notifysecctx(inode, attrs->ia_secdata,
  					    attrs->ia_secdata_len);
  	}
  
  	if (kernfs_type(kn) == KERNFS_DIR)
  		set_nlink(inode, kn->dir.subdirs + 2);
  }
  
  int kernfs_iop_getattr(struct vfsmount *mnt, struct dentry *dentry,
  		   struct kstat *stat)
  {
  	struct kernfs_node *kn = dentry->d_fsdata;
  	struct inode *inode = dentry->d_inode;
  
  	mutex_lock(&kernfs_mutex);
  	kernfs_refresh_inode(kn, inode);
  	mutex_unlock(&kernfs_mutex);
  
  	generic_fillattr(inode, stat);
  	return 0;
  }
  
  static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
  {
  	kernfs_get(kn);
  	inode->i_private = kn;
  	inode->i_mapping->a_ops = &kernfs_aops;
  	inode->i_mapping->backing_dev_info = &kernfs_bdi;
  	inode->i_op = &kernfs_iops;
  
  	set_default_inode_attr(inode, kn->mode);
  	kernfs_refresh_inode(kn, inode);
  
  	/* initialize inode according to type */
  	switch (kernfs_type(kn)) {
  	case KERNFS_DIR:
  		inode->i_op = &kernfs_dir_iops;
  		inode->i_fop = &kernfs_dir_fops;
  		break;
  	case KERNFS_FILE:
  		inode->i_size = kn->attr.size;
  		inode->i_fop = &kernfs_file_fops;
  		break;
  	case KERNFS_LINK:
  		inode->i_op = &kernfs_symlink_iops;
  		break;
  	default:
  		BUG();
  	}
  
  	unlock_new_inode(inode);
  }
  
  /**
   *	kernfs_get_inode - get inode for kernfs_node
   *	@sb: super block
   *	@kn: kernfs_node to allocate inode for
   *
   *	Get inode for @kn.  If such inode doesn't exist, a new inode is
   *	allocated and basics are initialized.  New inode is returned
   *	locked.
   *
   *	LOCKING:
   *	Kernel thread context (may sleep).
   *
   *	RETURNS:
   *	Pointer to allocated inode on success, NULL on failure.
   */
  struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
  {
  	struct inode *inode;
  
  	inode = iget_locked(sb, kn->ino);
  	if (inode && (inode->i_state & I_NEW))
  		kernfs_init_inode(kn, inode);
  
  	return inode;
  }
  
  /*
   * The kernfs_node serves as both an inode and a directory entry for
   * kernfs.  To prevent the kernfs inode numbers from being freed
   * prematurely we take a reference to kernfs_node from the kernfs inode.  A
   * super_operations.evict_inode() implementation is needed to drop that
   * reference upon inode destruction.
   */
  void kernfs_evict_inode(struct inode *inode)
  {
  	struct kernfs_node *kn = inode->i_private;
  
  	truncate_inode_pages(&inode->i_data, 0);
  	clear_inode(inode);
  	kernfs_put(kn);
  }
  
  int kernfs_iop_permission(struct inode *inode, int mask)
  {
  	struct kernfs_node *kn;
  
  	if (mask & MAY_NOT_BLOCK)
  		return -ECHILD;
  
  	kn = inode->i_private;
  
  	mutex_lock(&kernfs_mutex);
  	kernfs_refresh_inode(kn, inode);
  	mutex_unlock(&kernfs_mutex);
  
  	return generic_permission(inode, mask);
  }